1. Field of the Invention
Various embodiments of the invention relate primarily to non-planar bearings, bearing components, races, race components, and methods for making the same. More specifically, some embodiments of the invention include bearings and/or bearing races which have contact, rolling or sliding (or a combination of them) surfaces manufactured in whole or in part from diamond, cubic boron nitride and other superhard materials. Many types of diamond can be used, including natural diamond, monocrystalline diamond, polycrystalline diamond compacts, and diamond produced by chemical vapor deposition and physical vapor deposition processes. Embodiments of the invention include methods for making, shaping and polishing the diamond portion of the bearing or race, including diamond surfaces thereof. As used generally herein, the term “bearing unit” may include a bearing, race, balls, rollers, cups, cage, bushings, shafts, journals and/or any related components useful for rolling or sliding (or a combination of them) articulation with another part.
2. Description of Related Art
This section will discuss art related to non-planar bearings, bearing components, races, race components.
Various embodiments of this invention relate to the application of diamond and other super hard surfaces to bearings and bearing elements. These bearings and bearing elements include both sliding and rolling bearing elements and bearing races. Bearings are an essential part of a vast array of mechanical devices. In these various applications, bearings withstand high concentrated forces, direct impact loads, and must reduce friction and energy loss in mechanical devices. In addition, they must maintain mechanical alignment of parts and maintain precision and accuracy of mechanical devices. Any bearing application, whether a sliding or rolling (or a combination of sliding and rolling) bearing, which is subject to wear, high loads, high maintenance, and/or complex lubrication requirements will benefit from embodiments in the invention. Although embodiments of the invention have other applications as well.
Typical bearing types may include ball bearing with races, roller bearings with races or tracks, and sliding element bearings. All bearings may include radial or sleeve type bearings to maintain shaft alignment and thrust bearings to provide for axial force transmission. Roller bearings may perform the same types of functions and can include cylinder rollers, tapered rollers, needle rollers, barrel rollers (both symmetrical and asymmetrical). Sliding element bearings may include devices such as bushings, journals and ball bearing components and constrained articulating bearing components within mechanical devices.
Materials from which bearing components are fabricated depend upon the mechanical requirements for a specific application. Desirable properties for these materials include durability, resistance to fracture and wear, resistance to heat, low coeffecient of thermal expansion especially compared to typical metals used in bearings, low coefficient of friction for sliding contact with no lubricant and affinity for any lubricants which may be required to enhance the mechanical operation of the bearing. Various types of lubricants and lubrication systems may be used to enhance bearing operation and may increase the durability and longevity of function. The ability to function with little or no lubrication is desirable as lubricants add complexity to bearing systems.
Lubricants that might be used include; solid media such as graphite, molybdenum, PTFE, powdered media of the same compositions, fluid media, including water, hydrocarbons, fluorocarbons, halogenated hydrocarbons, complex hydrocarbons such as fats and fatty acids, silicone based lubricants and any other fluid. In some applications, fluids used for lubrication may be abrasive and/or corrosive, such as in oil well drilling apparatus, or corrosive fluid pumping systems.
Bearings may be called upon to perform many functions in a rotating, articulating or sliding animate or inanimate mechanical devices. These include, but are not limited to, sustaining high loads, maintaining precision of alignment, preserving a low coefficient friction for mechanical motion and enduring high impact shock loads. In addition, they must perform these various functions often in stressful environments, such as those entailing high temperature and or the presence of corrosive chemical agents, erosive environments or any other hostile environment.
An ideal material for bearing application would include having high hardness, high fracture toughness, low coefficient of mechanical friction, chemical inertness, thermal stability and high thermal conductivity. Current materials used to produce bearings and races include hard non ferrous alloys, hardened steels, ceramics, plastics (including polyethylene), and crystalline materials such as silicon carbide, titanium nitride and aluminum oxide. All of these materials are limited in their utility for this application due to their susceptibility to wear, deformation under load, susceptibility to fracture, degradation in corrosive environments and thermal breakdown.
Bearing wear or degradation results in loss of alignment of mechanical parts leading to further acceleration of wear and or disruption of other mechanical components, increased heat generation, further acceleration of bearing wear, with final catastrophic failure.
The ability of diamond to resistance wear exceeds that of all other materials. Further, diamond has desirable thermal stability, thermal conductivity, chemical inertness, and facture toughness to enhance bearing performance. The table below compares properties of polycrystalline diamond compact with some other materials from which bearing surfaces can be made.
TABLE 1COMPARISON OF DIAMOND TO OTHER MATERIALSThermalYoung'sBulkSpecificHardnessConductivityCTEModulusPossion'sModulusMaterialGravity(Knoop)(W/m K)(×10−6 in/in ° C.)(×106 psi)Ratio(×106 psi)Sintered3.5-4.0  7500-10,400900-26001.0-4.8120 0.7-0.2265-82PolycrystallineDiamondSintered3.483500-45008001.0-4.0100-1100.20-0.2255-65Cubic BoronNitrideSilicon3.002500844.7-5.3 580.1730CarbideAluminum3.50200087.8-8.853-550.2434-35OxideTungsten14.622001126.080-900.2248-54Carbide (10%Co)Cobalt8.20278-35111.2-14.311-1633-350.293-0.30627-30ChromeTi6Al4V4.43309 6.6-17.51115-170.26-0.3611-20Silicon Nitride3.2014.215.71.8-3.727-46 0.2-0.2715-33
A particular problem with prior art bearings is a tendency to develop catastrophic accelerated wear when a third body wear particle of sufficient hardness is introduced into the bearing environment.
The failures and pervasive limitations of the prior art show a clear need for improved bearings, bearing components, races, race components, and methods for making the same.